I adopt, and appreciate when others adopt a neutral/brutal tone.
"These lines have been repeated a number of places and probably ought to be pulled into a function called something like xyz in module zyq"
Generally your tone doesn't matter as long as it's not mean. "This is the 10th time I've told you declare constants FOR EVERY MAGIC NUMBER," does not belong in a code review; it belongs in feedback.
However there is something a bit dangling here which is linting and static analysis. If code has been repeated and genuinely ought to be pulled into a function, static analysis ought to be able to find this.
If you have already dealt with the broad class of possible change requests that can be caught by static analysis, the nature of the reviews should get a lot more straight forward. It will stay at a higher level and naturally tend toward verbiage like "I wonder if we ..." or, "I was thinking if ..."
In cases where static analysis would not find it for e.g. in the middle of a function doing something, we have several lines of code collecting data for some analytics event which is never repeated, but still confusing; I would say something like "For readability, could we pull the analytics bit into a separate function?"
Generally; if you can use "we" instead of "you" or "I"; I would prefer "we" in any team setting.
I second this, with emphasis. His videos cover the vast majority of topics at the intersection of math and hn. He has written custom software for the creation of the animations.